High efficiency gas infrared heater



Jan. 13,1970 E. J. COWAN 3,489,134

HIGH EFFICIENCY GAS INFRARED HEATER Filed Nov. 14, 1967 2 Sheets-Sheet 1 M Na *iw EDWIN J Cowq/v Q/AZ 107' TOENE s Jan. 13, 1970 E. J. COWAN HIGH EFFICIENCY GAS INFRARED HEATER 2 Sheets-Sheet 2 Filed NOV. 14, 1967 Eon/0v L. Con Aw United States Patent O 3,489,134 HIGH EFFICIENCY GAS INFRARED HEATER Edwin J. Cowan, 275 Manzanita, Sierra Madre, Calif. 91024 Filed Nov. 14, 1967, Ser. No. 682.796 Int. Cl. F24c 3/02; F2311 13/12 US. Cl. 12691 7 Claims ABSTRACT OF THE DISCLOSURE The disclosed gas infrared heater of very high thermal efliciency employs a burner having a multiple port head to the inlet side. of which an air-gas mixture is delivered .under pressure, the large number of small ports in the head passing the mixture for combustion at the outlet side of the head. Heat radiating tubing extends at the outlet side of the head to pass the hot gaseous flow in such mannor that the tubing is heated to at least 1,000 F. to radiate heat which is typically reflected. Problems of flashback and flame blow-out are eliminated; and a pilot burner need not be used, since a spark igniter may be utilized.

BACKGROUND OF THE INVENTION This invention relates generally to gas infrared heaters and more particularly concerns heaters of this type employing multiple port burners.

In the past, multiple port ceramic type infrared burners have been used for space heating and in various-heating environments. Direct and open exposure of such burners to spaces to be heated has been considered permissibly advantageous in one respect, since flame production remains close to perforated surfaces of the burners, which achieve high temperature and therefore emit infrared radiant energy at high intensity levels; however, they also suffer certain disadvantages which include a tendency for extremely hot exhaust gases to heat up adjacent areas whereby such heaters cannot be installed near somewhat combustible materials, such as wooden structural members. Also, operation of such burners is subject to disruption by wind, rain and snow conditions, which limits their use; they normally incorporate pilot burners, which waste gas and which can be extinguished by Wind conditions; and they suffer from relatively low (i.e. less than 55%) thermal efficiency operating characteristics.

Space heaters have also been constructed to employ heat radiating tubes within which flames are projected as by single port, gas jetting metal burners, in order to eliminate the problem of flame blow-out. Such burners have been thought necessary to the production of flames jetting a considerable distance within the tubes for effective heat transfer purposes; however, they are noisy in operation and suffer from occasional flashback creating an operating hazard. It can be seen, therefore, that prior heaters as described suffer disadvantages in use and operationand are not altogether satisfactory.

SUMMARY OF THE INVENTION It is a major object of the invention to provide heating apparatus combining the advantages of radiant tube heaters and multiple port burners, while eliminating their attendant disadvantages as described above. Basically, the gas infrared heater of the invention comprises a burner to which pressurized air is delivered by a blower, there being a combustible gas delivery orifice communicating with the burner interior; the burner including a head having an inlet side to which the gas and air in the duct are supplied under pressure, an outlet side, and a large number of relatively small cross section and generally parallel through openings directed to pass the gas and air forced therethrough for combustion at the outlet side;

3,489,134 Patented Jan. 13, 1 970 heat radiating tubing extending at the outlet side of the burner to receive and pass the hot gaseous flow therefrom in such manner that the tubing is heated to at least a dull red condition by flames and gases flowing downstream in the tubing; and a heat reflector located exteriorly of the tubing and at one side thereof to reflect heat radiated from the tubing toward the opposite side of the tubing. It is found that this combination of elements eliminates flash back, operates quietly and at high (up to 70%) thermal efiiciency, produces relatively low temperature exhaust gases at the discharge end of the tubing so that such gases do not create a combustion hazard, and that a gas pilot need not be used. As regards the latter, a spark producing igniter or plug may be carried for exposure to the outlet side of the burner head, whereby the problem of pilot gas wastage is eliminated.

Additional objects and advantages of the invention include the provision of control means operable to activate the spark plug when heater operation is initiated and to deactivate the plug in response to detection of gas and air combustion; the provision of a bafile plate structure in the tubing operable to direct the downstream flow of hot gases toward the inner wall of the tubing and to radiate heat through that wall; the provision of a baffle plate in the burner interior upstream of the burner head to deflect the combustible gas and air flow for inducing their intimate mixing at the inlet side of the head; the provision for sutficient flow of gas to mix with the air and combust for raising the temperature of the tubing to at least 1,000 E; and the provision of a 'dished and elongated reflector to receive the tubing, and a housing for the control appara tus integral with the reflector.

These and other objects and advantages of the invention, as well as the details of illustrative embodiments, will be more fully understood from the following detailed description of the drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a gas infrared heater incorporating the invention;

FIG. 2 is a plan view of the FIG. 1 heater taken on lines 22 of FIG. 1;

FIG. 3 is an end view of the heater taken on lines 33 of FIG. 2;

FIG, 4 is an elevation taken in section through the FIG. 1 heater;

FIG. 5 is a cross-section taken on lines 5-5 of FIG. 4; and

FIG. 6 is an enlarged elevation taken in section through a fragmentary portion of the heater adjacent of the burner.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawings, the heater basically comprises a burner incorporating a hollow body 10,to which air is supplied by a blower 11 illustrated as having an air inlet 12 and outlet 13, the latter communicating with the body interior 14. Combustible gas is also delivered tothe burner as via piping 15 penetrating the body 10 and an orifice 16 communicating with the burner interior.

As shown in FIG. 6, baffle plate structure may advantageously extend within the burner interior, in the path of the gas and air flow toward burner head 18 (containing portions 25) in order to direct the flow for inducing intimate mixing of the gas and air immediately upstream of the inlet side of the burner head 18. Such structure may for example include a first plate 17a extending crosswise of the duct immediately downstream of the orifice 16 so as to deflect the incoming combustible gas to flow radially outwardly and mix with the pressurized air stream delivered by the blower. In this regard the delivered air pressure in the burner interior 14 may for example be about .3 inch of water, and the gas pressure within the piping 15 may be higher than .3 inch of water, i.e. the normal service pressure at most gas outlets for commercial or residential use. While plate 17a has peripheral openings 20 to pass the flow, a second plate 17b downstream of plate 17a may have a central opening 21 for passing the flow. The combination of plates 17a and 1717 provides a labyrinth in the flow path to insure intimate mixing of the air and combustible gas prior to delivery to burner head 18, Mounting skirts may be provided on the plates as indicated at 19a and 19b.

The burner multiple porting is defined by a head 18 such as plate 22, having an inlet side 23, an outlet side 24 and a large number of relatively small cross section and generally parallel through ports or openings 25 directed to pass the air and gas mixture forced through the ports for combustion at the outlet side of the burner. In this regard, the plate 22 preferably extends crosswise of the body 10, and may be received in an enlarged annular portion 10a thereof as shown. Such a burner head may for example have 100 or more ports per square inch and the openings typically have cross sectional areas in sum, and at their outlets, greater than 20% of the wall surface area of the plate outlet side. Plate 22 may be ceramic.

Extending downstream from the burner is heat radiating tubing 27, the entrance to which is adjacent the burner head outlet side 24. The tubing 27 receives and passes the hot gaseous flow and flames 28 in such manner and under such normal operating conditions that the tubing is heated to at least about 1,000 F. In this regard, the elongated tubing may consist of aluminized steel, heated to at least a dull red condition, and may contain bafile means, such as the zig-zag strip 29 extending downstream and lengthwise of the tubing, for repeatedly deflecting the hot gaseous flow toward the inner wall 30 of the tubing for scavenging the boundary layer tending to collect at that wall. Such scavenging promotes better heat transfer to the inner wall both by conduction and also radiation from the hot baflle strip 29.

Located exteriorly of the tubing is a heat reflector 32 operable to reflect radiated heat toward the elongated outlet side 33 of the reflector. The latter is typically U-shaped (with diverging side walls) .in planes normal to the tube axis, and surrounds all but one elongated side of the tubing. At the extreme end 34 of the reflector is a deflector plate 35 in the path of warm gases discharging from the outlet end 27a of the tubing 27, for deflecting the latter in the direction indicated by arrow 36. However, it should be noted that the heat transfer characteristics of the heater are so favorable that normally the temperature of the warm gases at '36 is under l,000 F. Internal baffle 29 aids materially in this efliciency of heat extraction from the hot gases within tube 27.

An important aspect of the invention concerns the provision of a spark producing igniter exposed to the outlet side of the burner head 18, together with means to deliver high voltage current to the igniter. In the drawings, the igniter is shown in the form of a spark plug 38 having electrodes 39 within the tubing 27, and at one side therof, just downstream of the burner head 18. A suitable solid state circuit source of high voltage current pulses to the plug is indicated at 40 in FIG. 4. Current is supplied to the source 40 and to the blower motor 11a via lead 41.

Control means may also be provided to deactivate the current delivery source 40 in response to detection of gas and air combustion. Such a control means may take the form of a thermostat, indicated at 42, and electrically connected to the source 40 as via wiring 43. Plug 38 is shown as sealed in the tubing 27 at 44.

Advantageous features of the invention include luck of need for a pilot burner; very high thermal efliciency (as for example up to 70% thermal efficiency); absence of noisy operation and of flame flash back due to the use of the burner head 18; insurance against blow-out of the flame by fog or wind due to the enclosure of the flame within tube 27; pressure feed of air and combustible gas to insure adequate flame length within the tube 27 for maximum thermal eflrciency; and ability of the heater to operate in all positions with air powered combustion.

Finally it will be observed that the blower, mixing burner and circuitry 40 are received within a housing 50 that can be integral with the reflector 32. Mixing burner 100 may be mounted within a divider panel 51 separating the interior 52 of the reflector from the interior 53 of the housing 50. Wiring for the blower 11, plug 38 and source 40 is received within auxiliary housing structure 54 as shown. FIG. 2 indicates the provision of protective grillwork 55 across the outlet side of the reflector 32.

I claim:

1. In a gas infrared heater, the combination comprising a burner,

a blower communicating with the burner interior and operable to deliver pressurized air thereto,

means including a combustible gas delivery orifice communicating with the burner interior to deliver pressurized gas thereto,

said burner including a head having an inlet side to which a combustible air and gas mixture in said burner is supplied under pressure, an outlet side, and a large member of relatively small cross section and generally parallel through ports directed to pass the mixture forced therethrough for combustion at said outlet side,

battle plate structures forming labyrinth passage extents in the burner interior downstream of said orifice to deflect the combustible gas and air for intimate mixing thereof immediately upstream of said head inlet side,

heat radiating tubing extending with elongation at the outlet side of said burner to receive and pass the hot gaseous flow therefrom in such manner that the tubing is heated to at least about 1,000 F. by flames and gases flowing downstream in the tubing, the head extending crosswise of the duct so that the outlet side of said head faces the downstream interior of the tubing,

and a heat reflector located exteriorly of said tubing and at one side thereof to reflect heat radiated thereto and toward the opposite side of the tubing.

2. The combination of claim 1 wherein said bafile plate structure includes two plates extending crosswise of said interior and said gas delivery port opens toward said plate structure, said plates forming gas passing openings which are out of registration.

3. The combination of claim 1 including a spark producing igniter exposed to the outlet side of the burner head and means to delivery high voltage current pulses to said igniter.

4. The combination of claim '3 including control means operable to deactivate said current delivery means in response to detection of gas and air combustion.

5. The combination of claim 1 including bafile means in said tubing operable to deflect the flow of hot gases therein toward the inner wall of the tubing; and to radilate heat received from the burner toward said inner wal 6. The combination of claim 1 including means operable to supply suflic ient gas to said orifice to mix with said air and combust for raising the temperature of said tubing to a level such that the tubing is visibly red in color, the tubing comprising coated steel.

7. The combination of claim 1 wherein said reflector is dished and elongated for receiving said tubing and said reflector.

5 6 including a housing for said blower and integral with 3,199,505 8/ 1965 Lloyd 431-328 X 3,291,189 12/1966 Schade 431328 X References Cited 3,307,529 3/1967 Fannon et a1.

/1 2 g y 431328 5 CHARLES LMYHRE, Primary Examiner 10/1945 Hess 431328 X 8/1956 Cartter 12691 U.S.C1.X.R. 12/1962 Webster 431-328 X 431-328 

